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How to choose weight and size of ballasts for industrial photovoltaic systems
Ballasted structures for photovoltaics are today’s most popular solution for installing systems on flat or lightweight roofs, where mechanical fixings are not possible or not convenient. They are based on a simple principle: wind energy and static thrusts are counteracted by the weight of the ballast itself, preventing perforations of the waterproof sheathing and reducing the risks of infiltration.
Why choose ballasted structures for photovoltaic systems
Ballasted structures offer significant advantages over mechanically fixed systems. They eliminate the need to drill holes in the roof, simplify installation and reduce construction time. They also make it possible to lay on surfaces where anchoring is not allowed, such as sheathing roofs, bituminous roofing or synthetic membranes. In Mantiero systems for photovoltaic systems, the ballasted structure is designed to ensure load uniformity, even over large areas.
Modularity is another strength: the ballasts are set up to be mounted and dismounted without invasive intervention. This feature is particularly useful in industrial settings subject to frequent reconfigurations or roofing maintenance.
Ballast sizing and static checks
Photovoltaic ballast sizing starts with an environmental assessment: wind speed, exposure, panel tilt, and type of roofing. The main forces involved are the horizontal thrust and the tilting moment generated by the wind. In high-wind areas or on buildings with great height, ballasts should be increased in weight or arranged with higher density.
Each plant requires a balance between static weight and load-bearing capacity of the roof. The typical distributed load varies between 30 and 70 kg/m², but can rise to 100 kg/m² in cases of high-tilt installations or critical wind zones. The verification must ensure that the total load does not exceed the structural capacity of the roof.
| Panel tilt (°) | Wind speed (m/s) | Recommended minimum weight (kg/m²) | Notes |
|---|---|---|---|
| 10-15 | < 25 | 30-40 | Urban areas and protected covers |
| 20-25 | 25-35 | 50-70 | Standard industrial roofs |
| > 25 | > 35 | 80-100 | Coastal or mountainous areas |
Weight optimization and integrated ballast design
One of the most discussed issues in the design of ballasted structures for PV is weight optimization. Reducing the static load on the roof without compromising stability is a challenge that requires engineering approach. The principle is simple: there is no need to increase weight if you optimize the distribution and aerodynamics of the system.
Wind flow simulations show that proper module tilt (between 10° and 15°) reduces uplift thrusts by up to 25 percent, allowing lighter ballast with the same safety. Opposing row arrangements, so-called “east-west” systems, also balance wind forces and equalize roof loads.
Another key aspect is the integrated design between ballast and supporting structure. When the roof is made of steel or aluminum, the ballast can be distributed on continuous metal frames instead of insulated blocks, resulting in more uniform static behavior. This is the same logic applied in Mantiero load-bearing structures, where load distribution is designed to maintain balance even in wind or vibration conditions.
This vision makes it possible to reduce the total weight of the system by up to 20 percent, improve rollover safety, and simplify maintenance, while keeping the producibility of the PV system unchanged. In summary: efficiency is not only measured in kilowatts produced, but also in the amount of steel and concrete needed to support them safely.
Materials and types of ballast
PV ballasts can be made of concrete, galvanized steel or composite materials. Material choice affects weight, durability, and maintenance. Mantiero structures treated with galvanizing and protective paints ensure resistance even in corrosive environments or those subject to acid rain.
| Material | Specific gravity (kg/dm³) | Corrosion resistance | Typical application |
|---|---|---|---|
| Reinforced concrete | 2,4 | Good | Flat roofs, civil installations |
| Galvanized steel | 7,8 | Excellent | Large industrial plants |
| Composite or cemented plastic | 1,2 | Discrete | Lightweight or prefabricated roofs |
Operational steps and action plan
A ballasted structure installation project follows a strict operational plan with four main phases. The accuracy in each determines the overall stability of the system.
1. Structural survey and load verification
The bearing capacity of the roof is analyzed and critical points are mapped. In steel sheds, the load is distributed on the stringers or secondary profiles. It is essential to avoid localized weight concentrations that could deform plates or structural joints.
2. Layout modeling and ballast distribution.
Panel layout defines the geometry of the system. The ballasts are placed to balance the tipping forces. In large plants, rows of modules are connected by metal beams or cross profiles to distribute thrusts.
3. Assembly and stability verification
When laying, it is necessary to ensure that each ballast is in full contact with the surface and that the modules are tilted evenly. Precise levelling and alignment avoids aerodynamic load differences. In Mantiero load-bearing systems, the modularity of the profiles allows millimeter adjustments during assembly.
4. Inspection and maintenance
After installation, each plant should undergo periodic inspections to check the integrity of ballasts, joints, and anti-corrosion coatings. Six-monthly visual inspection and annual mechanical check of tightening torques is recommended.
Applications and industries
Ballasted structures for photovoltaics find application in a wide range of production contexts. Their adaptability makes them ideal for:
- Industrial sheds with flat or weakly sloping roofs, where direct fastening is not allowed.
- Agribusiness establishments and logistics centers, where roofs must remain waterproof and free of punctures.
- Installations on prefabricated steel roofs, where ballast distributes loads without changing the supporting structure.
- Commercial buildings and office centers with bituminous sheathing or PVC roofs, which cannot withstand rigid anchors.
- Coastal or high-wind environments where ballast weight becomes an active safety component.
The versatility of these structures allows tailor-made solutions: inclinations from 5° to 30°, modules arranged in single or opposing rows, with the possibility of combination with ground bearing structures for future extensions.
Durability and reliability of ballasted structures over time
Designing a PV ballasted structure means balancing precision and lightness, stability and flexibility. Weight is not the only decisive parameter: the distribution of loads, the quality of materials and the consistency with the roof define the real durability of the system. Every industrial plant has its own balance, and ballast becomes the key to maintaining it over time.
In an environment where efficiency and reliability are measured in years of service, engineering design and knowledge of materials are what distinguishes a solid plant from one destined to degrade. It is in this logic that Mantiero’s solutions for anti-corrosion structures and photovoltaic systems are born, designed to ensure long-term stability, durability and simplified maintenance.